Conventionally, a zeolite membrane, a carbon membrane, a titania membrane, and the like have been used as separation membranes disposed on a surface of a porous substrate. For example, known separation membrane-provided articles have included a zeolite membrane disposed as a separation membrane at a predetermined position on a porous substrate.
In a membrane separation by a zeolite membrane, recently, a membrane used for dehydration of organic solvent or biomass ethanol has been put into practical use. However, regarding the other uses, for example, separation of water from ethanol (ethanol condensation) in a biomass ethanol production process, separation of side chain hydrocarbon or aromatic hydrocarbon from linear chain hydrocarbon having a carbon number of 6 or more as a fuel component in petrochemistry or a petroleum refinery process, separation of inorganic gas from a linear chain hydrocarbon, or the like, development for the practical use is proceeded at present.
As membrane separation using a MFI type zeolite membrane, there is disclosed ethanol separation from a mixed liquid of ethanol and water (Patent Documents 1 and 2).
Patent Document 3 and Non Patent Document 1 disclose separation of a xylene isomer, where para-xylene is selectively permeated to block ortho-xylene and meta-xylene.
Patent Document 4 discloses separation of side-chain hydrocarbon from linear-chain hydrocarbon, and Patent Document 5 discloses separation of aromatic hydrocarbon from linear-chain hydrocarbon.
A serious problem against putting a zeolite membrane into practice lies in compatibility between permeability, and separability. Patent Documents 4 and 5 disclose usage of pores or gaps larger than the pores inherent to zeolite crystals as a measurement for solving the problem.
There is a statement that pores larger than the pores inherent to zeolite crystals have sizes of about a few nm in Non Patent Document 2. In addition, Non Patent Documents 2 and 3 disclose that, in a zeolite membrane having pores larger than the pores inherent to zeolite crystals, it is possible to separate side chain butane (isobutane) from liner chain butane (normal butane) which is a hydrocarbon isomer having a carbon number of 4.